Multiyear retrospective physiological assessment of sei whales (Balaenoptera borealis) from the South Atlantic

• Grant number: 22/03997-5
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: November 28, 2022
• End date: October 30, 2023
• Field of knowledge: Biological Sciences - Physiology - General Physiology
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Daniela Magalhães Drummond de Mello
• Supervisor: Charles Loren Buck
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Northern Arizona University, United States
• Associated to the scholarship: 21/00263-8 - Multiyear retrospective physiological assessment of Sei Whales (Balaenoptera borealis) from the South Atlantic, BP.PD

Abstract

Sei whales (Balaenoptera borealis) are one of the least studied species of whales; the combination of elusive behavior, broad home range, and deep-water preferences preclude systematic study for most populations. So far, no studies have been regularly conducted on this species, and its physiological and life history parameters remain obscure. A novel way to circumvent the afore mentioned challenges relies on the collection and analysis of baleen plates of deceased individuals. Baleen plates are continuous growing keratinized structures that constitute the baleen whale filter-feeding apparatus. As the baleen grows, it accumulates hormones and other endogenous circulating small molecules in a serial fashion. Through extraction and quantification of these molecules, one can harvest valuable biological data that can be used to retrospectively reconstruct physiological and behavioral patterns such as feeding preferences and migration habits through stable isotopes analysis, hormonal fluctuations associated with reproduction and stress, as well as exposure to contaminants. In this context, the present study aims to assess reproductive parameters, exposure to intrinsic and extrinsic stressors, and metabolic states of sei whales from the South Pacific Ocean through the quantification of progesterone, testosterone, 17²-estradiol, cortisol, corticosterone, aldosterone, and tri-iodothyronine (T3) in baleen samples from 35 individual whales. Mercury will be quantified to assess exposure to contaminants. Baleen plates were recovered at Golfo Tres Montes and Taitao Peninsula (between 47°S and 48°S), Chilean Patagonia, after the largest ever documented baleen whale stranding event in 2015. The baleen plates will be subsampled along their longitudinal axis and commercially available enzyme immunoassay kits will be used to assess expected/natural individual reproductive and metabolic hormone variation in relation to life history stage, as well as to detect potential anthropogenic and natural stressors that may have resulted in increased glucocorticoid hormones. Mercury content will be quantified to investigate potential of mercury exposure over time. The combination of the rare event of the stranding of hundreds of individual whales along with the recently created and validated technique to assess life histories of great whales through baleen analysis represents a unique opportunity to elucidate aspects of life history and exposure to anthropogenic stressors on this enigmatic and endangered species. (AU)